by Gabe Lacques, USA TODAY Sports

by Gabe Lacques, USA TODAY Sports

Their seasons just passed the one-quarter mark, so it's too soon for the San Francisco Giants and Washington Nationals to draw definitive conclusions when they size each other up Monday.

Yet both teams enter a three-game series at AT&T Park wondering if poor performances that seemed uncharacteristic might be the norm.

For the Giants, it is the grim showing of a starting rotation that was the bedrock of World Series championships in 2010 and 2012. Sunday, the Colorado Rockies beat them 5-0, the Giants' third loss in row and fifth in six games. Their starting pitchers were on the hook for all of the losses, and their 4.88 ERA ranks them 14th among 15 National League rotations.

"Is it a rough patch or a streak or a small sample? We'll see," manager Bruce Bochy told reporters Sunday before Barry Zito yielded five runs in 5 2/3 innings. "I will say it's been rough for those guys this week. But I think we need to get further before we can answer that question better."

Bochy said right-hander Ryan Vogelsong, who's 1-4 with an 8.06 ERA, has "had the toughest go-round."

Vogelsong might take solace in seeing the Nationals on Monday.

Heavy favorites to win the NL East, the Nationals fell to 23-21, 2 1/2 games behind the division-leading Atlanta Braves, with a 13-4 loss to the San Diego Padres. They rank 29th in the major leagues in batting average (.230) and on-base percentage (.292), are tied for 27th in runs (155) and are 28th in slugging (.373).

Right fielder Jayson Werth and catcher Wilson Ramos are on the disabled list and left fielder Bryce Harper was out of the lineup for a fourth time in six games since crashing into an outfield wall.

But poor performance - second baseman Danny Espinosa is batting .163- also has been a factor, as has inconsistency. First baseman Adam LaRoche has carried the Nationals during a 16-game hitting streak in which he's batting .382 with four home runs. But that streak was preceded by a 1-for-35 stretch.

"You have to have a lot of patience sometimes in this job," manager Davey Johnson said. "The middle of the lineup is swinging the bat very good, and other guys look like they're starting to come around. Sometimes it just takes time to jell."